Conventionally, as an ejector for a vapor compression refrigeration cycle, an ejector disclosed in Patent Literature 1 is known, for example.
This type of ejector includes (i) a nozzle that reduces a pressure of a refrigerant, which is after being compressed to have a high pressure by a compressor and then condensed and liquefied by a condenser, (ii) a suction portion for drawing a low-pressure refrigerant flowing out of an evaporator, and (iii) a diffuser for mixing the refrigerant injected from the nozzle and the refrigerant drawn into the suction portion and increasing a pressure of a mixed refrigerant.
In Patent Literature 1, the following characteristic structure is employed to provide an ejector that can exert a high nozzle efficiency without increasing a size of a structure irrespective of load variation of the refrigeration cycle. In the ejector in Patent Literature 1, a swirling space for swirling a refrigerant flowing into the swirling space through a refrigerant inflow port, from which a refrigerant flows in, is formed between the refrigerant inflow port and a nozzle passage in a body.
With this structure, by swirling of the refrigerant in the swirling space, a pressure of the refrigerant on a center side of a swirl can be reduced to a pressure at which the refrigerant becomes a saturated liquid-phase refrigerant or a pressure at which the refrigerant boils under reduced pressure and the refrigerant at the reduced pressure can be caused to flow into the nozzle passage that functions as a nozzle. Therefore, irrespective of the load variation of the refrigeration cycle, the refrigerant can be caused to boil under reduced pressure near a portion of the nozzle passage with the smallest passage area, which improves energy conversion efficiency (corresponding to the nozzle efficiency) in the nozzle passage.
In the ejector in Patent Literature 1, a passage forming member that forms the nozzle passage and a diffuser passage is disposed in a pressure reducing space and a pressure increasing space formed in the body and the passage forming member has a shape with a sectional area increasing as a distance from the pressure reducing space increases.
By employing the passage forming member in this shape, the diffuser passage can be formed in a shape diverging along an outer periphery of the passage forming member as a distance from the pressure reducing space increases. As a result, an axial dimension of the passage forming member can be prevented from increasing, and a size of the structure of the ejector can be prevented from increasing.
The ejector in Patent Literature 1 further includes a drive part for displacing the passage forming member. In Patent Literature 1, the drive part is configured by (i) a pressure responsive member that displaces the passage forming member according to a temperature and a pressure of the refrigerant flowing out of an evaporator and (ii) an elastic member that applies a load to push the passage forming member toward a side in a direction in which a sectional area of the refrigerant passage of the nozzle passage and the diffuser passage decreases.
By employing such a drive part, the passage forming member is displaced according to the load variation of the refrigeration cycle to adjust the passage areas of the nozzle passage and the diffuser passage, with which operation of the ejector appropriate to the load of the refrigeration cycle is achieved. The passage forming member is displaced to such a side as to increase the passage areas of the nozzle passage and the diffuser passage when a force from the pressure responsive member exceeds the load (i.e., biasing force) applied by the elastic member.